LA1837M

No.8271-5/9

Continued from preceding page.

Pin No.

Pin

Pin

voltage

Equivalent circuit

Pin function

10

AM narrow band

ceramic filter

connection

1.3V

Recommended narrow band ceramic filter

BFU450C4N (Murata Mfg. Co., Ltd.)

When the narrow band SD function is not used, bypass this circuit

by connecting a 50

Ω resistor and a 0.047µF capacitor in series.

11

FM S-meter

output

0V

RL = 8kΩ

12

AM S-meter

output,

AM SD

sensitivity

adjustment

0V (AM)

The AM SD sensitivity can be adjusted with an external resistor

between this pin and ground.

13

AM/FM IF buffer

output,

Output control

switch (muting

switch)

0V

V13

≤ 0.5V: Reception state

1.4V

≤ V13 ≤ 2.2V: IF buffer output on

V13

≥ 3.5V: IF buffer output and muting on

14

Phase

comparator

low-pass filter

(FM/AM

switching)

VCC-1.4

(FM)

0V (AM)

The IC switches to AM mode when this pin is connected to

ground through a resistor.

Resistor value limits: 2.7k

Ω (when VCC = 7V)

3.9k

Ω (8V) 5.1kΩ (9V)

6.2k

Ω (10V) 7.5kΩ (11V)

15

Pilot detector

low-pass filter

(Forced

monaural)

(VCO stop)

VCC-1.0

When a current of over 50µA is sourced by this pin, the IC

switches to forced monaural mode.

The VCO is stopped if this pin is connected to ground.

The resistor value limits are the same as for pin 14.

16

17

18

19

Post amplifier

I/O

Verg

Verg

Output impedance ro = 200Ω

Pin 16: right output, pin 17: left output

Inverting input pins

Pin 18: right input, pin 19: left input

RNF = 33kΩ

20

21

Multiplex output

3.5V

3.5V

Output impedance ro = 3.3kΩ

Pin 20: Right channel deemphasis

Pin 21: Left channel deemphasis

22

Multiplex input

2.9V

Input impedance ri = 20kΩ

23

FM

demodulated

output

2.8V (FM)

2.8V (AM)

Output impedance ro = 3.0kΩ

The separation can be adjusted with an external capacitor

connected between this pin and ground.

The VOsub/VOmain ratio is set to be approximately 0dB.

Continued on next page.